In the field of electric musical instruments such as electric guitars, basses and keyboards etc. small processing units, commonly referred to as effect pedals, are popular. They are designed to be disposed on the floor near the feet of the musician remote from the amplifier so that they may be easily switched on and off by means of foot switches generally located on their upper surfaces. Usually this type of pedal operates on 9 or 18 volts.
Commonly the power supply for these devices consists of one or more 9 volt batteries. As is well known batteries have a limited charge life. It therefore becomes frequently necessary to replace or recharge the batteries of effects which consume a large amount of power. This incurs a considerable expense and/or consumption of time.
The well known solution to the above problem is to employ an AC adapter which converts the relatively high voltage AC power commonly available from household wall outlets into the DC voltage required for the effect pedal.
The latter solution is commonly practiced but raises new problems of its own. The problems encountered with the AC adapter commonly employed in the prior art are related to the cords associated therewith. Specifically a shielded cable is required between the amplifier and the effect to transmit the audio signal output of the instrument to the amplifier. When an AC adapter is used for the effect pedal an additional cord is required to connect the effect pedal to the AC adapter. This generally adds to the clutter of cables in the area in which the musician is performing.
Compounding the above disadvantage is the fact that the most commonly used type of AC adapter comprises a relatively short coaxial cord for conducting the DC voltage output of the main body of the adapter unit to a female DC-in jack of the effect, and the main body of the adapter unit comprises rigid prongs protruding directly therefrom and designed to be inserted into a standard AC wall outlet. The result of this is that in actual practice there usually ends up being a coaxial AC cable extending midway into the performance space at which point it connects with the relatively bulky AC adapter and the path of power supply continues through the thinner DC conducting cables to the effect pedal. The preponderance of cables in this situation is not only unattractive but poses the hazard of tripping the musician and possible electric shock if the AC cables become worn or broken from being stepped on.
A further problem is that induction from the AC cables can cause noise in the form of sixty cycle hum in the audio cables when they are arranged in close proximity. Furthermore the need to arrange and transport the extra cables for the AC power is troublesome and adds to the set-up time required to prepare for a performance.
Thus the need for a convenient power supply system appropriate for use with DC powered effect devices is felt in the art of electric musical instruments.
It will be noted that in the art of electronics in general, composite cords for conducting signals and DC power are known. However in the known devices the terminal ends of the cables are almost invariably provided with rigid multi pin jacks in which the arrangement of pins is rigidly fixed in a pattern arbitrarily determined according to the make or model of the device. It will be further noted that in the art of musical instruments, the signal jacks are highly standardized so as to allow virtually any instrument to used with virtually any amp, and therefore from a practical standpoint departures from the established conventions are unacceptably inconvenient.